Remove unnecessary RCU grace period chaining #15

kernel-patches-bot · 2022-10-11T06:48:45Z

Pull request for series with
subject: Remove unnecessary RCU grace period chaining
version: 1
url: https://patchwork.kernel.org/project/rcu/list/?series=684412

kernel-patches-bot · 2022-10-11T06:48:46Z

Master branch: 4b9dfbb
series: https://patchwork.kernel.org/project/rcu/list/?series=684412
version: 1

Pull request is NOT updated. Failed to apply https://patchwork.kernel.org/project/rcu/list/?series=684412
error message:

Cmd('git') failed due to: exit code(128)
  cmdline: git am -3
  stdout: 'Applying: bpf: Free elements after one RCU-tasks-trace grace period
Patch failed at 0001 bpf: Free elements after one RCU-tasks-trace grace period
When you have resolved this problem, run "git am --continue".
If you prefer to skip this patch, run "git am --skip" instead.
To restore the original branch and stop patching, run "git am --abort".'
  stderr: 'error: sha1 information is lacking or useless (kernel/bpf/memalloc.c).
error: could not build fake ancestor
hint: Use 'git am --show-current-patch=diff' to see the failed patch'

conflict:

kernel-patches-bot · 2022-10-20T14:40:51Z

Master branch: fa70e60
series: https://patchwork.kernel.org/project/rcu/list/?series=685353
version: 2

kernel-patches-bot · 2022-10-20T14:45:53Z

Master branch: fa70e60
series: https://patchwork.kernel.org/project/rcu/list/?series=685353
version: 2

kernel-patches-bot · 2022-10-20T15:09:05Z

Master branch: fa70e60
series: https://patchwork.kernel.org/project/rcu/list/?series=685353
version: 2

kernel-patches-bot · 2022-10-20T15:14:45Z

Master branch: fa70e60
series: https://patchwork.kernel.org/project/rcu/list/?series=685353
version: 2

kernel-patches-bot · 2022-10-20T15:20:21Z

Master branch: fa70e60
series: https://patchwork.kernel.org/project/rcu/list/?series=685353
version: 2

kernel-patches-bot · 2022-10-20T15:25:56Z

Master branch: fa70e60
series: https://patchwork.kernel.org/project/rcu/list/?series=685353
version: 2

kernel-patches-bot · 2022-10-20T15:31:33Z

Master branch: fa70e60
series: https://patchwork.kernel.org/project/rcu/list/?series=685353
version: 2

kernel-patches-bot · 2022-10-20T15:37:08Z

Master branch: fa70e60
series: https://patchwork.kernel.org/project/rcu/list/?series=685353
version: 2

kernel-patches-bot · 2022-10-20T15:42:52Z

Master branch: fa70e60
series: https://patchwork.kernel.org/project/rcu/list/?series=685353
version: 2

kernel-patches-bot · 2022-10-20T16:09:00Z

Master branch: fa70e60
series: https://patchwork.kernel.org/project/rcu/list/?series=685353
version: 2

kernel-patches-bot · 2022-10-20T16:15:10Z

Master branch: fa70e60
series: https://patchwork.kernel.org/project/rcu/list/?series=685353
version: 2

kernel-patches-bot · 2022-10-20T16:21:18Z

Master branch: fa70e60
series: https://patchwork.kernel.org/project/rcu/list/?series=685353
version: 2

kernel-patches-bot · 2022-10-20T16:27:32Z

Master branch: fa70e60
series: https://patchwork.kernel.org/project/rcu/list/?series=685353
version: 2

kernel-patches-bot · 2022-10-20T16:33:39Z

Master branch: fa70e60
series: https://patchwork.kernel.org/project/rcu/list/?series=685353
version: 2

As an accident of implementation, an RCU Tasks Trace grace period also acts as an RCU grace period. However, this could change at any time. This commit therefore creates an rcu_trace_implies_rcu_gp() that currently returns true to codify this accident. Code relying on this accident must call this function to verify that this accident is still happening. Reported-by: Hou Tao <[email protected]> Signed-off-by: Paul E. McKenney <[email protected]> Cc: Alexei Starovoitov <[email protected]> Cc: Martin KaFai Lau <[email protected]>

The memory free logic in bpf memory allocator chains a RCU Tasks Trace grace period and a normal RCU grace period one after the other, so it can ensure that both sleepable and non-sleepable programs have finished. With the introduction of rcu_trace_implies_rcu_gp(), __free_rcu_tasks_trace() can check whether or not a normal RCU grace period has also passed after a RCU Tasks Trace grace period has passed. If it is true, freeing these elements directly, else freeing through call_rcu(). Signed-off-by: Hou Tao <[email protected]>

Local storage map is accessible for both sleepable and non-sleepable bpf program, and its memory is freed by using both call_rcu_tasks_trace() and kfree_rcu() to wait for both RCU-tasks-trace grace period and RCU grace period to pass. With the introduction of rcu_trace_implies_rcu_gp(), both bpf_selem_free_rcu() and bpf_local_storage_free_rcu() can check whether or not a normal RCU grace period has also passed after a RCU-tasks-trace grace period has passed. If it is true, it is safe to call kfree() directly. Signed-off-by: Hou Tao <[email protected]>

To support both sleepable and normal uprobe bpf program, the freeing of trace program array chains a RCU-tasks-trace grace period and a normal RCU grace period one after the other. With the introduction of rcu_trace_implies_rcu_gp(), __bpf_prog_array_free_sleepable_cb() can check whether or not a normal RCU grace period has also passed after a RCU-tasks-trace grace period has passed. If it is true, it is safe to invoke kfree() directly. Signed-off-by: Hou Tao <[email protected]>

kernel-patches-bot · 2022-10-20T16:39:51Z

Master branch: fa70e60
series: https://patchwork.kernel.org/project/rcu/list/?series=685353
version: 2

kernel-patches-bot added merge-conflict new rcu-dev V1 labels Oct 11, 2022

kernel-patches-bot force-pushed the rcu-dev branch from 5ca9bde to f965c82 Compare October 13, 2022 18:38

kernel-patches-bot added V2 and removed V1 labels Oct 14, 2022

kernel-patches-bot force-pushed the rcu-dev branch 4 times, most recently from 996bf5c to 00c153b Compare October 18, 2022 23:12

adding/updating ci files

87e7989

kernel-patches-bot removed the merge-conflict label Oct 20, 2022

kernel-patches-bot force-pushed the series/684412=>rcu-dev branch from 112760b to 7745abd Compare October 20, 2022 14:41

kernel-patches-bot force-pushed the rcu-dev branch from 87e7989 to fa70e60 Compare October 20, 2022 14:44

kernel-patches-bot force-pushed the series/684412=>rcu-dev branch from 7745abd to 3f7d87e Compare October 20, 2022 14:45

kernel-patches-bot force-pushed the series/684412=>rcu-dev branch from 3f7d87e to 5e0d56c Compare October 20, 2022 15:09

kernel-patches-bot force-pushed the series/684412=>rcu-dev branch from 5e0d56c to 0892932 Compare October 20, 2022 15:14

kernel-patches-bot force-pushed the series/684412=>rcu-dev branch from 0892932 to cbbf01f Compare October 20, 2022 15:20

kernel-patches-bot force-pushed the series/684412=>rcu-dev branch from cbbf01f to c98ad5b Compare October 20, 2022 15:26

kernel-patches-bot force-pushed the series/684412=>rcu-dev branch from c98ad5b to 2c30954 Compare October 20, 2022 15:31

kernel-patches-bot force-pushed the series/684412=>rcu-dev branch from 2c30954 to 05b5b6c Compare October 20, 2022 15:37

kernel-patches-bot force-pushed the series/684412=>rcu-dev branch from 05b5b6c to 260938f Compare October 20, 2022 15:42

kernel-patches-bot force-pushed the series/684412=>rcu-dev branch from 260938f to a23361c Compare October 20, 2022 16:09

kernel-patches-bot force-pushed the series/684412=>rcu-dev branch from a23361c to 323b6f8 Compare October 20, 2022 16:15

kernel-patches-bot force-pushed the series/684412=>rcu-dev branch from 323b6f8 to bc6d7cc Compare October 20, 2022 16:21

kernel-patches-bot force-pushed the series/684412=>rcu-dev branch from bc6d7cc to 759167c Compare October 20, 2022 16:27

kernel-patches-bot force-pushed the series/684412=>rcu-dev branch from 759167c to 2f582b5 Compare October 20, 2022 16:33

paulmckrcu and others added 4 commits October 20, 2022 09:39

kernel-patches-bot force-pushed the series/684412=>rcu-dev branch from 2f582b5 to 32140fa Compare October 20, 2022 16:39

Remove unnecessary RCU grace period chaining #15

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